E30 Zone

Hi all after having my ex kumho 325i laid up for a couple of years( got married) I've decided to take the bull by the horns and stroke the engine. My reasons for a stoker are many and I've considered m30s m52 etc but I'd like to stroke my M20 since i have stuff like enlarge baffled sump M21 oil pump and other goodies,it currently runs a lightened flywheel a throttle body set up with Weber Alpha management and a Cat cam 284 it made 190 hp on Thor engineering hub type RR,
My question is do I buy a full on IE 2.9 stroker kit for £1500 ish or go down the DIY route and source an M52 crank and buy new 130 mm Rods? I have access to all the machining resources I need and have built plenty of engines before, I'm not in a hurry, but I can see the value in buying a kit with bolts shells rods etc all in good condition ready to assemble, I know m52 cranks are easy enough to buy but then I'll need shorter rods and will probably end up having to buy new rods since I can't imagine 320 rods are easy to come by anymore
best advice please
Cheers Simon

why stop at 2.9L if going to IE? you can do a ~3.1L for the same cost and for both you would want a 135mm rod from M5x to keep costs down.

all else equal torque is a function of displacement and a 3.1L is the biggest practical size with 85mm bore

if you end up going with IE do the OEM piston dish-dome style which is a recent addition.

it will be cheaper to do m52 crank 130mm rods (find a set and get them checked and refurbed dont buy brand new) and b25 slugs for a 2.8L which is a common budget setup.

http://www.e30zone.net/e30zonewiki/inde ... ding_a_2.8

Ok thanks for your help on that, m52 cranks are common enough but secondhand 130 mm rods seem sparse, I won't need to get the block decked with th M52 crank will I? I guess I need to throw out the CATCam? It's a 284 and I lost a lot of top end power when I changed to it but gained good torque I suppose the duration on the higher compression engine wants to be significantly different, does anyone have an idea on good Cams for a 2.8 M52 set up ( standard valved 885 head on Throttle bodies )

nominally 0.5mm from the top of block is needed to get proper CR and squish but it is something that needs to be measured properly as IMO it is something worth paying attention to and different heads and blocks measure out slightly different. aim for 1.0mm clearance between the top of piston angled dome and angled section on head. with a gasket of 1.75mm or 2.05mm this means pistons are slightly above deck about 0.5mm or a bit more

im in oz and i bought a used of 130mm rods from the uk so shouldnt be an issue finding them 325E, 320i, 323i all had 130mm rods plus the 5 series with eta lump. new would cost a bomb and aftermarket would be cheaper and better anyway

catcams 284 should have good topend and midrange but little bottom end like all catcams. i have one and seen about 5 or so stroker dyno plots and think catcams suck for the street, leave them for track guys. on throttle bodies something high 270's will be good with the CR you will get from a 2.8L. the schrick 284/272 works well but i dont like a split duration on these things but it still works well. if i was doing a 2.7 or 2.8L with 10:1CR id be tempted to find out if schrick can do a 284/284

massaged head is worth doing if you find someone who knows what works on the 885 head as it doesnt need much work to make alot better.

3.1 M20 strokers are quick and sound awesome. Here's a vid of one in a track car at Kaylami (South Africa) showing up an E92 M3. Plays with it for a bit, then overtakes and disappears into the distance. Overtake at 6:20ish.

I should clarify that this car is a track machine only, it has no V5 and was built from parts for the kumho series. (Not by me) Saying that I prefer mid range torque to top end power, as I have found that in damp conditions and ESP with inexperienced mates driving its very easy to spin an E30 with hard race suspension and a very cammy engine. Also the original cam was some kind of alpina one, It gave terrible midrange but good top range- 197fwhp on a hub dyno and the car was still making power at 7200 rpm when the ecu limiter cut in
The problem was that with the 325i sport box it bogged terribly between 2nd and 3rd gear,as there was a terrible torque trough at 3000 ish rpm after rebuilding the top end, lap times improved with less hp at the top but greater mid range torque.

So since a 3.0 litre stroker IE kit looks fairly expensive and will probably necessitate brake upgrade
I guess a 2.8 DIY job will do

alpina cam usually gives a nice bottom end and midrange than a aftermarket camshaft but on a stroker peak power is at a lower rpm than it is on a stock 325i so i wouldnt call it a topend cam at all. the alpina is high 260's low 270's advertised duration

you should certainly have more topend with the catcams 285 than a genuine alpina cam but the alpina will be alot stronger on the bottom end. if not there sounds like something is setup wrong or it wasnt an alpina cam at all.

this is an alpina cam vs schrick 288



if you find a set of high CR b25 pistonsthis will net a CR over 10:1 so use a schrick 288 for the track but plan on deepening the valve pockets

Motorhole wrote:3.1 M20 strokers are quick and sound awesome. Here's a vid of one in a track car at Kaylami (South Africa) showing up an E92 M3. Plays with it for a bit, then overtakes and disappears into the distance. Overtake at 6:20ish.

That noise

Thanks for the Cam info Reggid the original cam was in poor condition ( lobe surface startingvto break up) and resulted in a terrible bottom and mid range it did say Alpina on the end of it I think but who knows, may it was dialled in on the vernier resulting in the poor bottom end ( ill find the old dyno sheet scan some at some point) Im going to pull my 325 bottom end apart today , how do I tell if its the lower or higher compression pistons I have?

Measure them

http://www.e30zone.net/e30zonewiki/inde ... 20#Pistons

Paynts wrote:Thanks for the Cam info Reggid the original cam was in poor condition ( lobe surface startingvto break up) and resulted in a terrible bottom and mid range it did say Alpina on the end of it I think but who knows, may it was dialled in on the vernier resulting in the poor bottom end ( ill find the old dyno sheet scan some at some point) Im going to pull my 325 bottom end apart today , how do I tell if its the lower or higher compression pistons I have?

'

block number 256E1 or something is higher CR, where as 256K2 is lower comp (i assume the K is Katayser or catalytic onverter) 25 means 2.5L, 6 is 6 cycl. or the depth of valve reliefs for exhaust side they will be slightly bigger

Haha yes E zone wiki !!! Yup I've got the HC ones I measured them against the engine wiki measurements and they are correct

I've had an email back from a guy with 2 litre rods and I've got a crank sorted so its a goer!
The only thing that worries me is getting the finished engine to run with my current EMU and map its a webber Alpha system and needs to be mapped by a dealer on An RR Also should I go for bigger injectors? I'm running on throttle bodies